Interactive input systems that allow users to inject input (i.e. digital ink, mouse events etc.) into an application program using an active pointer (e.g. a pointer that emits light, sound or other signal), a passive pointer (e.g. a finger, cylinder or other suitable object) or other suitable input device such as for example, a mouse or trackball, are known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 and in U.S. Patent Application Publication No. 2004/0179001, all assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the entire disclosures of which are incorporated herein by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; laptop and tablet personal computers (PCs); smartphones, personal digital assistants (PDAs) and other handheld devices; and other similar devices.
Above-incorporated U.S. Pat. No. 6,803,906 to Morrison et al. discloses a touch system that employs machine vision to detect pointer interaction with a touch surface on which a computer-generated image is presented. A rectangular bezel or frame surrounds the touch surface and supports imaging devices in the form of digital cameras at its corners. The digital cameras have overlapping fields of view that encompass and look generally across the touch surface. The digital cameras acquire images looking across the touch surface from different vantages and generate image data. Image data acquired by the digital cameras is processed by on-board digital signal processors to determine if a pointer exists in the captured image data. When it is determined that a pointer exists in the captured image data, the digital signal processors convey pointer characteristic data to a master controller, which in turn processes the pointer characteristic data to determine the location of the pointer in (x,y) coordinates relative to the touch surface using triangulation. The pointer coordinates are conveyed to a computer executing one or more application programs. The computer uses the pointer coordinates to update the computer-generated image that is presented on the touch surface. Pointer contacts on the touch surface can therefore be recorded as writing or drawing or used to control execution of application programs executed by the computer.
In some interactive input systems, conventional projection units are employed to project a computer-generated image onto a surface with which a user interacts. For example, U.S. Pat. No. 6,540,366 to Keenan et al., assigned to SMART Technologies ULC, discloses an overhead projection system comprising an overhead projector support assembly extending generally horizontally from a generally vertical support surface. A touch-sensitive display screen having a display surface is mounted on the support surface beneath the projector support assembly. A projector is mounted on the projector support assembly adjacent its distal end and is aimed to project images onto the display surface of the touch-sensitive display screen. The touch-sensitive display screen outputs control signals in response to contacts made thereon. The control signals are then conveyed to a personal computer, which uses the control signals to update the application program being executed and to update the image projected onto the touch-sensitive display surface by the projector.
U.S. Pat. No. 6,281,878 to Montellese discloses an input device for detecting input with respect to a reference plane. The input device includes a light source, a light sensor and a processor. The light source provides a plane of light adjacent to a reference plane, such as a solid surface of a desktop, on which an input template image of a keyboard is projected by a projector. The light sensor, having an acute angle with respect to the reference plane, senses light reflected by an object, such as a finger, close to the plane of light and generates a signal indicative of sensed light. The processor determines a position of the object with respect to the reference plane based on response of the sensor.
U.S. Patent Application Publication No. 2011/0242060 to McGibney et al. entitled “Interactive Input System And Information Input Method Therefor” filed on Apr. 1, 2010 and assigned to SMART Technologies, ULC, discloses an interactive input system comprising at least one imaging assembly having a field of view looking into a region of interest and capturing image frames and processing structure in communication with the at least one imaging assembly. When a pointer exists in captured image frames, the processing structure demodulates the captured image frames to determine frequency components thereof and examines the frequency components to determine at least one attribute of the pointer.
U.S. Pat. No. 6,219,011 to Aloni et al. discloses an image projection based display apparatus using cameras to capture images of a display surface. The cameras capture a plurality of reference lines that are used to calibrate a plurality of images. The apparatus can also detect the distortion of the reference lines and apply a correction.
Although the above-mentioned interactive input systems enhance the reliability of determining pointer location, being able to resolve pointer location during sporadic system displacement is desired. It is therefore an object to provide a novel interactive input system and method.